Compatibilization and elastomer toughening of polyamide‐6 (PA6)/poly(phenylene ether) (PPE) blends

In the elastomer‐modified (polyamide‐6/poly(phenylene ether) (PA6/PPE) = 50/50 blends, poly(styrene‐co‐maleic anhydride) (SMA) was demonstrated to be an efficient reactive compatibilizer. The G1651 elastomer was shown to be an effective impact modifier to result in superior toughness and heat‐deflection temperature (HDT) than is the 1901X elastomer for the SMA‐compatibilized blends because G1651 particles exclusively reside within the dispersed PPE phase but 1901X particles tend to distribute in the PA6 matrix and/or along the interface. The apparent average diameter of the dispersed PPE phase is insignificantly dependent on the elastomer content in the G1651‐modified blend, whereas it increases with increase of the elastomer content in the 1901X‐modified blend. Moreover, there exists a critical elastomer content, 15 phr, for the ductile–brittle transition of the G1651‐modified SMA‐modified PA6/PPE blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 23–32, 1999     

Fracture toughness characterizations of compatibilized polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends

Under the plane-strain condition, the material properties, K_IC and G_IC, of the blends, brittle or with small-scale yielding, increase with increasing elastomer content. To evaluate the critical J-integral for the ductile blends, several methods have been compared to understand the influence of elastomer content and different thicknesses using single-edge notch-bend specimens. For a given thickness, the fracture toughness increases with increasing elastomer content. Moveover, the slope of the R-curve becomes gradually steeper with increasing elastomer content and decreasing specimen thickness. J_IC values determined from ASTM E813-89 and modified ASTM E813-81 methods always give the highest and the lowest values, respectively. J_IC values determined from three other methods are comparable and can be employed to characterize the fracture toughness of the compatibilized PA6/PPE blends. It is noted that J_IC values determined from the modified ASTM E813-89 and the hysteresis energy methods are apparently independent of thickness. Therefore, these two methods may be considered as potential alternative techniques to evaluate the critical J-integral for toughened polymer blends.     

Morphology of injection molded modified poly(phenylene oxide)/polyamide‐6 blends

The morphology of injection molded poly(phenylene oxide)/polyamide‐6 blends was investigated. A distinct skin layer, subskin layer, and core region were found across the part thickness, and the morphology of the skin layer was clearly observed. The shape and size of the dispersed phase depended on the position across the part thickness and the viscosity ratio of the component polymers. For low viscosity ratios, small and large particles coexisted in the subskin layer, implying that both coalescence and breakup of the dispersed phase occurred in that layer. For high viscosity ratios, an intermediate zone, in which little deformation of the dispersed phase occurred, was found between the skin layer and the subskin layer. These findings are expected to help foster understanding of the mechanism of morphology evolution during the filling and cooling stages of the injection molding process.     

Polymer blends of PA6 and PPE compatibilized by poly[methylene (phenylene isocyanate)] (PMPI) coupler

An oligomeric isocyanate, poly[methylene(phenylene isocyanate)] (PMPI), is demonstrated to be an efficient reactive compatibilizer for blends of polyamide-6 (PA6) and poly(2,6dimethyl-1, 4-phenylene ether)(PPE). Use of this compatibilizer results in substantial improvements in mechanical properties. The multiple functional isocyanate acts as a coupling agent and reacts with PA6 and PPE endgroups during melt processing to produce a PA6-co-PMPI-co-PPE mixed copolymer at the interface. This in situ-formed copolymer tends to reside at the interface to reduce the melt interfacial tension and enhance interface adhesion.     

XPS surface studies of injection-molded poly(phenylene ether)/nylon 6,6 and poly(phenylene ether)/HIPS blends

The surface compositions of a series of poly(phenylene ether)/nylon 6,6 blends (PPE/PA), and PPE/HIPS blends, prepared by melt compounding and injection molding, have been quantitatively measured using XPS. For PPE/PA blends, the surface is dominated by the PA component for blends containing more than 25 wt % PA in the bulk. The enrichment of the PA component, which is actually the component of highest surface free energy, is rationalized in terms of the bulk morphology that consists of PPE domains in a PA continuous phase. Blends prepared by reactive extrusion processes, which form compatibilizing PPE/PA copolymers, show a decrease in surface PA enrichment with increasing copolymer content in the final blend. PPE/HIPS blends have a surface composition equal to the formulated value over the entire composition range, for both molded and solvent cast blends. The addition of 5% PVME to a 60/40 PPE/HIPS blend results in a molded surface containing 35–40 wt % PVME. © 1992 John Wiley & Sons, Inc.     

Study on morphology of compatibilized poly (vinyl chloride)/ultrafine polyamide‐6 blends by styrene–maleic anhydride

Ultrafine polyamide‐6 (UPA6) with a size of 4–8 μm was prepared via jet‐milling. Blends of poly (vinyl chloride) (PVC) and UPA6 using a reactive copolymer styrene–maleic anhydride (SMA‐18%) were prepared. The change in morphology and structure of the blends were studied using differential scanning calorimetry, scanning electron microscopy, and X‐ray diffraction. The blend behavior was also determined experimentally using dynamic mechanical analysis. Contrasted to the original PA6, the crystallinity of the UPA6 decreased, the size of its crystallites were reduced, and its melting point decreased to 175°C. In all blends, PVC formed the continuous matrix phase. SMA is miscible with PVC and tends to be dissolved in the PVC phase during the earlier stages of blending. The dissolved SMA has the opportunity to react with PA6 at the interface to form the desirable SMA‐g‐PA6 copolymer. This in situ formed SMA‐g‐PA6 graft copolymer tends to anchor along the interface to reduce the interfacial tension and results in finer phase domains. Cocrystallity existed in PVC/(UPA6/SMA) at a ratio of 82/(18/5). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 850–854, 2005     

Investigation on the crystallization behavior of poly(ether ether ketone)/poly(phenylene sulfide) blends

The morphology of nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with poly (ether ether ketone) (PEEK) have been observed by polarized optical microscope (POM) equipped with a hot stage. The nonisothermal crystallization behavior of PPS and PEEK/PPS blend has also been investigated by differential scanning calorimetry (DSC). The maximum crystallization temperature for PEEK/PPS blend is about 15°C higher than that of neat PPS, and the crystallization rate, characterized by half crystallization time, of the PEEK/PPS blend is also higher than that of the neat PPS. These results indicate that the PEEK acts as an effective nucleation agent and greatly accelerates the crystallization rate of PPS. The Ozawa model was used to analyze the nonisothermal crystallization kinetics of PPS and its blends. The Avrami exponent values of neat PPS are higher than that of its blend, which shows that the presence of PEEK changed the nucleation type of PPS from homogeneous nucleation to heterogeneous nucleation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Weldline morphology of injection molded modified poly(phenylene‐oxide)/polyamide‐6 blends

The weldline morphology of modified‐poly(phenylene‐oxide)/polyamide‐6 blends has been investigated. A distinct contacting layer consisting of fine spherical particles was observed from the V‐notch at the surface to the center of the molded part for the low viscosity ratio blend. In contrast, such small particles were not found and a slight deformation was observed near the part's surface for the high viscosity ratio blend. The weldline morphology was found to be dominated by the deformation, the breakup, and the relaxation of the dispersed modified‐poly(phenyleneoxide) phase. The effect of injection conditions on the weldline morphology has also been investigated. The morphology of the meldline was quite complicated. Distorted multi‐layered structures were observed. It was found that those structures arise from the subsequent flow after merging of the two flow fronts. Weldlines and meldlines have been studied separately, and their formation mechanisms were found to be basically similar.     

Phase behavior and morphology of poly(phenylene ether)/epoxy blends

The miscibility of diglycidyl ether of bisphenol-A (DGEBA) based epoxies with a series of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) resins was measured and the effects of PPE molecular weight, end-capped or grafted functionality, and blend composition were explored. Interpretation of phase behavior was aided by the use of the Flory-Huggins theory. Miscibility behavior in the unreacted blends was found to correlate with trends in phase separation during the curing reaction. The cured morphologies of these blend systems were also studied. The compatibilization effect of PPE-epoxy copolymer formation was found to play a dominant role in determining the final size of the dispersed phase, while temperature control of reaction and mass transfer kinetics were identified as a possible means of further affecting the cured morphology.     

Tensile behaviour and fracture toughness of poly(ether ether ketone)/poly(ether imide) blends

Summary The bulk tensile behaviour of poly(ether ether ketone) and poly(ether imide) homopolymers and their blends has been investigated, and the temperature and strain rate dependence of the yield stress discussed in terms of simple Eyring rate theory. In fracture mechanics tests, the K_IC of PEEK was found to decrease significantly with increasing test speed, whereas the K_IC of PEI showed little rate sensitivity. Therefore, although a gradual increase in K_IC with increasing PEEK content was observed in the blends at low loading rates, this effect was anticipated to be less pronounced at higher loading rates.     

Polymer blends of PA6 and PPE compatibilized by phenolic novolac epoxy coupler

A commercially available multi-functional epoxy monomer, phenolic novolac epoxy (PNE) resin, has demonstrated to be an effective reactive compatibilizer for the blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). It requires about 1/10 by weight relative to a typical conventional reactive compatibilizer to achieve same level of compatibilization in terms of mechanical property improvements. By acting as a coupler, this multi-functional epoxy can react with PA6 and PPE during melt blending and produces the desirable PA6-co-PNE-co-PPE mixed copolymers at the interface. This in situ-formed copolymer containing PA6 and PPE segments tends to reside at the interface between PA6 and PPE domains to reduce melt interfacial tension and enhance interface adhesion as an efficient compatibilizer of the PA6/PPE blends.     

Super‐toughness in compatibilized poly(butylene terephthalate)/poly(ethylene‐octene) copolymer blends

Poly(butylene terephthalate) (PBT)/poly(ethylene‐octene) (PEO) blends containing 1.0 wt% epoxy and from 0 to 30 wt% PEO were obtained by extrusion and injection molding. The blends were composed of two pure amorphous phases. The observed torque increases showed that epoxy reacted with PBT, leading to a fine and homogeneous morphology up to 15 wt% PEO content, which appeared larger and more heterogeneous at higher PEO contents. Toughness values fifteen‐fold those of pure PBT were obtained with only 13 wt% PEO. The tensile properties, including ductility, decreased with increasing PEO content, indicating that the adhesion level necessary for high ductility is higher than that necessary for super‐toughness. The inter‐particle distance (τ) was the main parameter that controlled toughness. The comparison of the results of this work with those of the same PBT/PEO blends with two different compatibilizers provides additional strong evidence of the adhesion at the interphase as the main parameter that controls the critical τ in these modified thermoplastic/rubber blends.     

Thermally crosslinkable poly(phenylene sulfide)/poly(ether sulfone)/polymerization of monomer reactant–polyimide blends

The effects of thermally crosslinkable polymerization of monomer reactant–polyimide (POI) on the miscibility, morphology, and crystallization of partially miscible poly(ether sulfone) (PES)/poly(phenylene sulfide) (PPS) blends were investigated with differential scanning calorimetry and scanning electron microscopy. The addition of POI led to a significant reduction in the size of PPS particles, and the interfacial tension between PPS and crosslinked POI was smaller than that between PES and crosslinked POI. During melt blending, crosslinking and grafting reactions of POI with PES and PPS homopolymers were detected; however, the reaction activity of POI with PPS was much higher than that with PES. The crosslinking and grafting reactions were developed further when blends were annealed at higher temperatures. Moreover, POI was an effective nucleation agent of the crystallization of PPS, but crosslinking and grafting hindered the crystallization of PPS. The final effect of POI on the crystallinity of the PPS phase was determined by competition between the two contradictory factors. The crosslinking and grafting reactions between the two components was controlled by the dosage of POI in the blends, the premixing sequence of POI with the two components, the annealing time, and the temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2906–2914, 2002; DOI 10.1002/app.10287     

Effect of processing conditions and reactive compatibilizer on the morphology of injection molded modified poly(phenylene oxide)/polyamide‐6 blends

The effect of injection molding conditions and reactive compatibilization on the morphology of maleic anhydryde‐modified poly(phenylene oxide)/polyamide‐6 blends was investigated. The injection flow rate primarily influenced the position of the subskin layer, and the injection temperature affected the aspect ratio of the dispersed phase. A reduction of the sue of the dispersed phase occured during the converging flow in the barrel‐to‐sprue zone. The reactive compatibilization reduced the flow induced deformation, the coalescence and the breakup of particles and improved the dispersion of the minor phase.     

Polymer blends of polyamide-6 and poly(phenylene oxide) compatibilized by styrene-co-glycidyl methacrylate

Incompatible polymer blends between polyamide-6 (PA6) and poly(phenylene oxide) (PPO) have been compatibilized in situ by the styrene-glycidyl methacrylate (SG) reactive copolymers. The epoxy functional groups in SG copolymers can react with the PA6 amine and carboxylic endgroups at interface to form various SG-g-PA6 copolymers. These in situ-formed grafted copolymers tend to anchor along interface to function as compatibilizer of the blends. The styrene and the SG segments of the grafted copolymers are miscible (or near miscible) with PPO; whereas the PA6 segments are structurally identical with PA6 phase. The compatibilized blend, depending on quantity of the compatibilizer addition and the glycidyl methacrylate (GMA) content in the SG copolymer, results in smaller phase domain, higher viscosity, and improved mechanical properties. About 5% GMA is the optimum content in SG copolymer that produces the best compatibilization of the blends. This study demonstrates that SG reactive copolymers can be used effectively in compatibilizing polymer blends of PA6 and PPO. © 1996 John Wiley & Sons, Inc.     

The vibration welding of poly(phenylene oxide)/poly(phenylene sulfide) blends

The weldability of three blends of poly(phenylene oxide) and poly(phenylene sulfide), each with a different level or type of impact modifier, is assessed through 120 and 240 Hz vibration welds. The type of impact modifier is shown to have a large effect on the strength and ductility of welds. Weld strength in these blends is shown to be sensitive to the weld frequency; higher weld strengths are attained at the higher weld frequency. In these three blends, maximum relative weld strengths of about 70%, 85%, and 87% have been demonstrated at a weld frequency of 240 Hz. The highest weld strength in each of these three blends is achieved at different weld pressures.     

Microcellular foaming of poly(phenylene sulfide)/poly(ether sulfones) blends using supercritical carbon dioxide

Microcellular foaming of poly(phenylene sulfide)/poly(ether sulfones) (PPS/PES) blends presents a promising approach to produce high‐performance cellular materials with tailored microstructures and enhanced properties. This study investigated the effects of multiphase blend composition and process conditions on the foaming behaviors and final cellular morphology, as well as the dynamic mechanical properties of the solid and microcellular foamed PPS/PES blends. The microcellular materials were prepared via a batch‐foam processing, using the environment‐friendly supercritical CO₂ (scCO₂) as a blowing agent. The saturation and desorption behaviors of CO₂ in PPS/PES blends for various blend ratios (10 : 0, 8 : 2, 6 : 4, 5 : 5, 4 : 6, 2 : 8, and 0 : 10) were also elaborately discussed. The experimental results indicated that the foaming behaviors of PPS/PES blends are closely related to the blend morphology, crystallinity, and the mass‐transfer rate of the CO₂ in each polymer phase. The mechanisms for the foaming behaviors of PPS/PES blends have been illustrated by establishing theoretical models. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42634.     

Effects of heat treatment on the properties of heterogeneous cation permeable membranes from blends of poly(ether sulfone)/sulfonated poly(phenylene sulfide) and phenolphthalein poly(ether ether ketone)/sulfonated poly(phenylene sulfide)

The effects of heat treatment on the properties of membranes prepared from blends of poly(ether sulfone)/sulfonated poly(phenylene sulfide) (SPPS) and phenolphthalein poly(ether ether ketone)/SPPS were studied in detail. The membranes' fundamental properties, including water content, transport number, diffusion coefficient of electrolytes, flux, and so on, changed with both treated temperature and time, whereas the ion‐exchange capacity and electrical resistance remained approximately unchanged. The trends may have been due to the possible structural change resulted from the shrinking of the polymers forming the membranes. Furthermore, the membranes also retained a good physical appearance at temperatures below 220°C. Therefore, a series of heterogeneous membranes with desired conductivities and selectivities as well as proper water contents, which could satisfy different industrial purposes, such as electrodialysis, diffusional dialysis, and proton exchange, were achieved by simple heat treatment for a proper time and at a proper temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 494–499, 2005     

Confined crystallization phenomena in immiscible polymer blends with dispersed micro- and nanometer sized PA6 droplets, part 2: reactively compatibilized PS/PA6 and (PPE/PS)/PA6 blends

In this paper the relation between the blend phase morphology and the fractionated crystallization behavior of PA6 in reactively compatibilized immiscible PS/PA6 and (PPE/PS)/PA6 immiscible blends is studied. Reactive compatibilization is used as an effective tool for controlling the blend phase morphology, and to reduce the PA6 dispersed droplet size. As reactive compatibilizers, SMA2 and SMA17 are used, which differ in their level of miscibility with the amorphous PS and (PPE/PS) components. With SMA2 a strong shift of PA6 crystallization to much higher supercoolings than before is found after compatibilization resulting in crystallization at temperatures as low as 85 °C. This is ascribed to the strong decrease of the droplet sizes down to 100-150 nm. Nucleation experiments show that heterogeneous bulk nucleation can be reintroduced in the submicron-sized PA6 droplets by adding enough nucleating agents of sufficient small size. The degree of fractionated crystallization is found to depend on the interface between PA6 droplets and surrounding medium, as it is influenced by vitrification of the matrix polymer and by the location of the compatibilizers SMA2 and SMA17. The method used for mixing the reactive compatibilizer with the blend components also affects the fractionated crystallization process.